Nuclear Friday: New Lives for Silver Bullets

If you’ve heard anything about current US nuclear weapons programs, you’ve heard of the expensive B61 Mod-12. When completed, each bomb will cost more than its weight in gold. There are other controversies besides just the price. The B61, once known under the informal code name “Silver Bullet”, has been around a long time and is just the latest and most expensive part of the Stockpile Stewardship program.

The B61 was expensive when it was first developed back in the 1960’s too, but no one cared. Something like the Cuban Missile Crisis makes the public not care. The B61 was designed as a small, light, variable yield, thermonuclear device primarily carried by light tactical attack aircraft, and even fighters if need be. It could obliterate a forward command post with a stealthy under the radar laydown strike of 300 tons, higher yield laydown or airburst strikes, or loft or high altitude strikes with a full yield of 340 kilotons. It was intended to be bomb that could do almost everything. The B61 could remain stable even when pickled (released) in supersonic flight. Its predecessor, the B43 could not do this.

It cost a lot of money, but the B61 eventually worked. Here’s a video from 1967 that explains why the the B61 cost so much, but ended up working so well. The B61 became the mainstay of tactical range bombs in the seventies and eighties, and is the only light tactical weapon on active deployment with US forces in Europe. You don’t need to watch it, but I hope that any readers of The Board who care about the Mod-12 program will watch it. It’s 26 minutes, so skip it if you want to.

This is from the 1998 release of old films from the Atomic Energy Commission. Notice how the video blacks out at 9:05 during the discussion of testing the fission primary? All these videos are censored. They still provide the best information possible about the early days of the B61 and I recommend that anyone critical of Mod-12 watch this. I’m critical of Mod-12 too, but perhaps in different ways which I will explain later.

“You dropped a bomb on me, Baby…” 

The B61 Mod-12 has been described as a nuclear bunker buster, but it’s not designed to penetrate bunkers before exploding like you may have seen guided conventional bombs do so often in footage from Operation Desert Storm. The B61 is tough, and the Mod-12 version is tougher, but it’s probably impossible to make a nuclear bomb robust enough to survive penetration of the heaviest bunkers. Instead, it will penetrate the ground next to the target and then explode several meters below the surface. The surrounding soil and rock will transmit shock waves that destroy the target.

This isn’t a new idea, but in WWII the RAF had to do it the hard way.


That’s a Grand Slam, the heaviest conventional bomb ever made, being dropped from a modified Lancaster. The Grand Slam and the similar but smaller Tall Boy were used to attack the most heavily hardened German targets with a good measure of success. Many V-1 and V-2 weapons were destroyed at their hardened launch sites RAF 617 also used these weapons to destroy the v-3 multi-chambered gun. They didn’t know what they were bombing, but they figured that if it had that much reenforced concrete around it, it must be worth bombing.

Obviously, a nuclear bunker buster has some huge advantages over large bombs like these. The B61 Mod-12 weighs around 700 pounds, and has a yield around 50 kilotons. I’m not completely certain about that number as the Mod-12 is a very secret program. This figure is based on earlier modifications of the B61. Given the accuracy of the Mod-12, 50kT is plenty.

But how is it so accurate? If you watched the video above, they showed some laydown tests. That’s one way to assure accurate delivery, but the Mod-12 isn’t designed for an all-out Cold War style nuclear exchange. It’s a modern weapon for a risk averse age. Furthermore, a laydown strike would give the bomb no ground penetrating ability as the  bomb would not hit at a sharp enough angle and would be slowed by its drag parachute. The video does mention that the original B61 had a radar in the nose. That was just a radar altimeter, not part of a guidance system. The B61 was purely a ballistic drop and laydown weapon. Mod-12, is guided, sort of. It’s complicated.

“I am guided by the beauty of our weapons” 

So, how is it guided? We are going to have to take a short excursion into guidance systems and countermeasures to understand how the Mod-12 probably works. Notice I said “probably”. This is super secret stuff, but I think I can make a good guess.

I mentioned Desert Storm earlier. Most of the footage you saw of guided bombs destroying bunkers and bridges were infrared images of weapons using the Paveway guidance system.


Paveway dates back to the early seventies. The system is easily identified by the fin assembly on the front of the bomb. The system usually requires laser target designation, though there is also a version with a little video transmitter in the front that the pilot uses to fly the bomb to the target. The laser is easier to use as all the pilot has to do is keep the laser in the aircraft pointed at the target, and the bomb will fly itself. Ground troops can also carry laser target designators to assist attacking planes.

The main problem with Paveway is that it requires the pilot to keep attention on the target until the bomb hits. It would be easier if the pilot could simply drop the bombs and forget them. Because of this, Paveway was largely replaced by JDAM.


JDAM came out in the mid-90’s and is GPS for bombs. You just program the bombs with  where you want them to go, fly them in into a zone where their guidance will be able to get them to the target, drop the bombs, and retreat. This is a much simpler system for pilots to use and it is not limited by the range of targeting lasers.

JDAM does have its problems. GPS systems can be jammed. Military GPS is harder to jam than the GPS in a car, but it can be done. This is why JDAM is sometimes combined with a laser system. You can see the laser receiver in this picture.


Now all this is very interesting, but there’s one big reason I don’t believe the B61 Mod-12 uses either of these systems.

“You spin me round round…” 

There are two different air drop tests in this official 2015 video release from Sandia National Labs. The drops start at 2:15 and both show me that Mod-12 uses an almost entirely new form of guidance.

It SPINS! There’s no way a guidance system like JDAM could make fine enough adjustments to the fins to cope with that spin. I am persuaded that once the Mod-12 starts spinning it falls with no guidance at all. And there’s sure no way it can have any optics in that solid nose.

So how does it work? How can it be so accurate? Here’s my best guess: I think the Mod-12 does have a GPS system similar to JDAM. In the closeups in the video, it looks like the fins are not movable, but Sandia isn’t going to give away all their secrets. I think Mod-12 gets a sense of where it is using GPS well outside the range of jamming, makes a few small adjustments to its flight, then spin stabilizes itself and falls unguided.

I am convinced the Mod-12 has to have some kind of internal guidance because it’s sometimes described as a standoff weapon, a weapon that can be delivered from far away with little risk to the pilot. The US already has a small number of Mod-11 earth penetrating weapons that were made from earlier versions of the B61 back in 1997. The Mod-12 is different in that it has lower yield, deeper penetration ability, and can be lofted from a longer distance from the target. Long range lofting simply has to have guidance to be this accurate.

BTW, the spin stabilization is not new to Mod-12. We don’t see any spinning bombs in the 1967 video in this post because all it shows is a laydown test. If you spin a bomb and then lay it down, it will bounce in unpredictable ways. The video does mention a spin rocket at 18:50 and shows parts of it, so I think the earliest B61’s had a spin setting for drop and loft delivery, and a no-spin setting for laydown.

Also, you might note that there were some missile tests at the end of the  2015 video. The Minuteman was probably disinformation, but the Trident launch was relevant. The UK is planning to refit some of their Trident D5’s with earth penetrating guided warheads by 2019. Some of the Mod-12 systems will be used in this warhead.


One of the main concerns about the Mod-12 is that it costs its weight in gold. This can’t really be avoided. It would certainly be cheaper to build a new weapon with these capabilities rather than reworking an old one, but this really isn’t possible. The US has not entered into major arms control talks with any nation since Boris Yeltsin was president of Russia. Both nations agreed to make no new nuclear weapons, though treaties do allow for making certain modifications of existing weapons. The Mod-12 program stretches the limits of these agreements. Russia has not made any official complaints however much Russia Today complains.

I would like to see renewed Cold War style arms talks aimed at substantial reductions in world stockpiles of nuclear weapons. I also think that powers entering into such talks should have the power to manufacture entirely new nuclear weapons systems as long as these new weapons are offset by large reductions in older stockpiles. I don’t think Putin is really interested in this, and United States foreign policy attention is directed elsewhere.

The other controversy, which you can learn more about in this PBS New Hour video, is the Mod-12 is too good. Well, that’s not the words they use, but that’s what they are saying. The idea is that the Mod-12 is too clean, and too effective at performing its precise role. What? Are they really saying that it’s bad because it kills too few people? Would it be better if it killed more people? The objection is that the Mod-12 lowers the threshold for using nuclear weapons, that the Mod-12 is too tempting to use.  I’m sorry, but I think it’s good to have options short of mass slaughter.

In the PBS video a general tries to explain that the Mod-12 is a valuable part of an overall system of deterrence, but I don’t think he’s really being honest. I say what he was not allowed to say, something you probably already know. The B61 Mod-12 is designed for a preemptive counterforce strike against North Korea should the need arise. It would also be very effective against any nuclear armed non-state actor, should we face the threat of nuclear terrorism.

I have stated here on The Board that I believe the Nuclear Taboo is important, but there may be times when using a nuclear weapon becomes necessary. It is good to have precise and effective counterforce options in such dire circumstances. Mod-12, the new life of the Silver Bullet, may be just the bomb the world needs.










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